1 Media Subsystem Profile 2 ======================= 3 4 Overview 5 -------- 6 7 The media subsystem covers support for a variety of devices: stream 8 capture, analog and digital TV streams, cameras, remote controllers, HDMI CEC 9 and media pipeline control. 10 11 It covers, mainly, the contents of those directories: 12 13 - drivers/media 14 - drivers/staging/media 15 - Documentation/admin-guide/media 16 - Documentation/driver-api/media 17 - Documentation/userspace-api/media 18 - Documentation/devicetree/bindings/media/\ [1]_ 19 - include/media 20 21 .. [1] Device tree bindings are maintained by the 22 OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS maintainers 23 (see the MAINTAINERS file). So, changes there must be reviewed 24 by them before being merged via the media subsystem's development 25 tree. 26 27 Both media userspace and Kernel APIs are documented and the documentation 28 must be kept in sync with the API changes. It means that all patches that 29 add new features to the subsystem must also bring changes to the 30 corresponding API files. 31 32 Due to the size and wide scope of the media subsystem, media's 33 maintainership model is to have sub-maintainers that have a broad 34 knowledge of a specific aspect of the subsystem. It is the sub-maintainers' 35 task to review the patches, providing feedback to users if the patches are 36 following the subsystem rules and are properly using the media kernel and 37 userspace APIs. 38 39 Patches for the media subsystem must be sent to the media mailing list 40 at linux-media@vger.kernel.org as plain text only e-mail. Emails with 41 HTML will be automatically rejected by the mail server. It could be wise 42 to also copy the sub-maintainer(s). 43 44 Media's workflow is heavily based on Patchwork, meaning that, once a patch 45 is submitted, the e-mail will first be accepted by the mailing list 46 server, and, after a while, it should appear at: 47 48 - https://patchwork.linuxtv.org/project/linux-media/list/ 49 50 If it doesn't automatically appear there after a few minutes, then 51 probably something went wrong on your submission. Please check if the 52 email is in plain text\ [2]_ only and if your emailer is not mangling 53 whitespaces before complaining or submitting them again. 54 55 You can check if the mailing list server accepted your patch, by looking at: 56 57 - https://lore.kernel.org/linux-media/ 58 59 .. [2] If your email contains HTML, the mailing list server will simply 60 drop it, without any further notice. 61 62 63 Media maintainers 64 +++++++++++++++++ 65 66 At the media subsystem, we have a group of senior developers that 67 are responsible for doing the code reviews at the drivers (also known as 68 sub-maintainers), and another senior developer responsible for the 69 subsystem as a whole. For core changes, whenever possible, multiple 70 media maintainers do the review. 71 72 The media maintainers that work on specific areas of the subsystem are: 73 74 - Remote Controllers (infrared): 75 Sean Young <sean@mess.org> 76 77 - HDMI CEC: 78 Hans Verkuil <hverkuil@xs4all.nl> 79 80 - Media controller drivers: 81 Laurent Pinchart <laurent.pinchart@ideasonboard.com> 82 83 - ISP, v4l2-async, v4l2-fwnode, v4l2-flash-led-class and Sensor drivers: 84 Sakari Ailus <sakari.ailus@linux.intel.com> 85 86 - V4L2 drivers and core V4L2 frameworks: 87 Hans Verkuil <hverkuil@xs4all.nl> 88 89 The subsystem maintainer is: 90 Mauro Carvalho Chehab <mchehab@kernel.org> 91 92 Media maintainers may delegate a patch to other media maintainers as needed. 93 On such case, checkpatch's ``delegate`` field indicates who's currently 94 responsible for reviewing a patch. 95 96 Submit Checklist Addendum 97 ------------------------- 98 99 Patches that change the Open Firmware/Device Tree bindings must be 100 reviewed by the Device Tree maintainers. So, DT maintainers should be 101 Cc:ed when those are submitted via devicetree@vger.kernel.org mailing 102 list. 103 104 There is a set of compliance tools at https://git.linuxtv.org/v4l-utils.git/ 105 that should be used in order to check if the drivers are properly 106 implementing the media APIs: 107 108 ==================== ======================================================= 109 Type Tool 110 ==================== ======================================================= 111 V4L2 drivers\ [3]_ ``v4l2-compliance`` 112 V4L2 virtual drivers ``contrib/test/test-media`` 113 CEC drivers ``cec-compliance`` 114 ==================== ======================================================= 115 116 .. [3] The ``v4l2-compliance`` also covers the media controller usage inside 117 V4L2 drivers. 118 119 Other compilance tools are under development to check other parts of the 120 subsystem. 121 122 Those tests need to pass before the patches go upstream. 123 124 Also, please notice that we build the Kernel with:: 125 126 make CF=-D__CHECK_ENDIAN__ CONFIG_DEBUG_SECTION_MISMATCH=y C=1 W=1 CHECK=check_script 127 128 Where the check script is:: 129 130 #!/bin/bash 131 /devel/smatch/smatch -p=kernel $@ >&2 132 /devel/sparse/sparse $@ >&2 133 134 Be sure to not introduce new warnings on your patches without a 135 very good reason. 136 137 Style Cleanup Patches 138 +++++++++++++++++++++ 139 140 Style cleanups are welcome when they come together with other changes 141 at the files where the style changes will affect. 142 143 We may accept pure standalone style cleanups, but they should ideally 144 be one patch for the whole subsystem (if the cleanup is low volume), 145 or at least be grouped per directory. So, for example, if you're doing a 146 big cleanup change set at drivers under drivers/media, please send a single 147 patch for all drivers under drivers/media/pci, another one for 148 drivers/media/usb and so on. 149 150 Coding Style Addendum 151 +++++++++++++++++++++ 152 153 Media development uses ``checkpatch.pl`` on strict mode to verify the code 154 style, e.g.:: 155 156 $ ./scripts/checkpatch.pl --strict --max-line-length=80 157 158 In principle, patches should follow the coding style rules, but exceptions 159 are allowed if there are good reasons. On such case, maintainers and reviewers 160 may question about the rationale for not addressing the ``checkpatch.pl``. 161 162 Please notice that the goal here is to improve code readability. On 163 a few cases, ``checkpatch.pl`` may actually point to something that would 164 look worse. So, you should use good sense. 165 166 Note that addressing one ``checkpatch.pl`` issue (of any kind) alone may lead 167 to having longer lines than 80 characters per line. While this is not 168 strictly prohibited, efforts should be made towards staying within 80 169 characters per line. This could include using re-factoring code that leads 170 to less indentation, shorter variable or function names and last but not 171 least, simply wrapping the lines. 172 173 In particular, we accept lines with more than 80 columns: 174 175 - on strings, as they shouldn't be broken due to line length limits; 176 - when a function or variable name need to have a big identifier name, 177 which keeps hard to honor the 80 columns limit; 178 - on arithmetic expressions, when breaking lines makes them harder to 179 read; 180 - when they avoid a line to end with an open parenthesis or an open 181 bracket. 182 183 Key Cycle Dates 184 --------------- 185 186 New submissions can be sent at any time, but if they intend to hit the 187 next merge window they should be sent before -rc5, and ideally stabilized 188 in the linux-media branch by -rc6. 189 190 Review Cadence 191 -------------- 192 193 Provided that your patch is at https://patchwork.linuxtv.org, it should 194 be sooner or later handled, so you don't need to re-submit a patch. 195 196 Except for bug fixes, we don't usually add new patches to the development 197 tree between -rc6 and the next -rc1. 198 199 Please notice that the media subsystem is a high traffic one, so it 200 could take a while for us to be able to review your patches. Feel free 201 to ping if you don't get a feedback in a couple of weeks or to ask 202 other developers to publicly add Reviewed-by and, more importantly, 203 ``Tested-by:`` tags. 204 205 Please note that we expect a detailed description for ``Tested-by:``, 206 identifying what boards were used at the test and what it was tested.
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